The California Supreme Court today blocked a proposal that would split the state into three from reaching the November ballot, according to multiple sources.

The state’s high court said the measure, Proposition 9, shouldn’t be on the ballot because of the “substantial” questions raised about its validity. The court issued a brief order saying it intervened because the potential harm from permitting the measure to remain on the ballot outweighs any possible damage caused by delaying the measure for a future election.

The Planning and Conservation League filed a lawsuit arguing that the proposition amounted to a change to the state’s Constitution. As such, it requires a two-thirds vote of both legislative chambers before the matter could be put to voters.

Backed by billionaire venture capitalist Tim Draper, Proposition 9 would carve the state into thirds: Northern California, encompassing San Francisco and 39 other counties; California, sweeping in Los Angeles and five adjacent counties; and Southern California, including San Diego.

Draper argued in court papers that the initiative would give voters more say.

The court asked Alex Padilla, California’s secretary of state, and Draper to explain to the court by Aug. 20 why a conservation group’s request to block the measure shouldn’t be granted. Draper will have 30 days to respond.